A Massachusetts General Hospital study in next week's Psychiatry Research: Neuroimaging shows marked brain changes over an eight-week practice of mindfulness meditation. Of course, by definition, every experience you have makes changes in your brain (that's pretty much the definition of experience: "something that changes your brain"), but in this case, the changes point to deep and lasting effects as a result of meditation that correspond to the reported experience of meditators. (This confirms earlier research from the hospital, like this study from 2005).